The invention relates to a method of determining the roll angle position of a rotating flying body relative to a fixed station with the aid of a laser light beam emitted by the fixed station and received by the flying body. The invention further relates to an apparatus for performing the method.
In rotating projectiles in which a flight path correction is performed during flight, the roll angle of the projectile typically must be determined with respect to a (frequently earth-bound) reference value in order to ignite the corresponding correction charge at the correct position.
It is already known to determine the roll angle by means of magnetic sensors. In this method, a magnetic sensor connected to the projectile periodically intersects different field lines of the geomagnetic field as the projectile rotates, so that a periodic signal which is characteristic for the rpm of the projectile results at the sensor output. However, in order to obtain an unambiguous allocation of the angular position of the projectile to an earth-bound reference system, it is necessary to dispose a magnet in the region of the barrel muzzle of the firing or launch apparatus. This magnet transmits or transfers a corresponding reference signal to the projectile as it exits the barrel.
The disadvantages of roll angle determination using magnetic sensors are the relatively high costs and the relatively high wear of the muzzle magnet.
Also known are optical/visual methods of determining the roll angle of the flying body. These methods employ a laser beam, which is being used as a guide beam for the flying body anyway, and make use of the polarization of this guide beam. The rotation of the flying body is detected by the change in intensity of the received radiation that passes through a rotating polarization filter (analyzer) connected to the flying body. Since the angular position of the flying body can only be determined with modulo 180.degree. in this case, an unambiguous allocation of the projectile coordinates to a (e.g., earth-bound) reference system is likewise necessary at the beginning of the firing process. This allocation can be achieved by the lateral arrangement of a transmitter in the firing device, and with a second, laterally offset detector in the flying body. The latter fixes the position of the projectile in the immediate vicinity of the weapon. Thereafter, the position is determined through counting of the polarization transmissions.
A disadvantage shared by this arrangement is the relatively high outlay or cost for equipment; in particular, an additional transmitter must be provided in the firing apparatus.
A number of methods of determining the roll angle position are also conceivable; with a typical prerequisite of these methods being that the flying body always move in a path that is coaxial with the guide beam. Thus, for example, a non-mirror-symmetric screen on the side of the laser and a corresponding screen on the side of the flying body could be brought into the beam path of the guide beam, with the screens being configured such that a maximum brightness would only result behind the screen on the side of the flying body if the two identically-shaped screens were oriented parallel to one another. A coaxial arrangement of the guide beam and the receiver, however, represents the exception, and therefore cannot usually be a prerequisite.